One type of mass storage device is a disc drive data storage system. Disc drive data storage systems include, for example, one or more magnetic or optical storage discs. In disc drives which include multiple storage discs, the discs are mounted on a spindle for co-rotation about a central axis. Each disc surface has an associated head slider (or “head”) which includes a transducer for reading data from the disc surface. Data is stored on the disc surface in circular, concentric data tracks. A “cylinder” is the set of tracks (one per each disc surface) which have the same radius from the central axis.
The data format on the disc drive is laid out in a form such that sequential addresses follow a track. At the end of a track either a head switch is performed to address the same track on an adjacent surface (another track in the same cylinder), or a track switch is performed to access an adjacent track on the same surface. This creates a serpentine track format. If the head switch takes a higher priority over the track switch (i.e., head switches are performed whenever possible), the format is called “head serpentine.” On the other hand, if track switch is taken before head switch, the format is called “track serpentine.” As the track density has increased significantly over the past years, the track pitch becomes increasingly smaller. As a result, the time to finish a track switch is now significantly smaller than that of a head switch, and the track serpentine format has become the preferred data format.
In head serpentine and track serpentine formats, the track and head numbers experience periodically increasing and decreasing order. The inconsistency of monotonicity causes significant computational inefficiency that is connected to the track or head numbers. This is especially true in cases where certain tables that are indexed by the track or head numbers must be searched. It is very likely that the entries in those tables must be checked one by one from the very beginning toward the ending point, until all targets have been found. As a results, efficient search algorithms, such as a binary search, cannot be employed. As the table size gets large, such searching consumes quite a lot of computation time and resources. This in turn adversely effects the performance of the drive.
Embodiments of the present invention provide solutions to these and/or other problems, and offer other advantages over the prior art.